From a888cf3e5934c79d8edfca69dfe7fbe8f52c7476 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 3 Nov 2020 12:39:01 +0100 Subject: [PATCH 334/347] ptrace: fix ptrace_unfreeze_traced() race with rt-lock Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz [ Upstream commit 0fdc91971b34cf6857b4cfd8c322ae936cfc189b ] The patch "ptrace: fix ptrace vs tasklist_lock race" changed ptrace_freeze_traced() to take task->saved_state into account, but ptrace_unfreeze_traced() has the same problem and needs a similar fix: it should check/update both ->state and ->saved_state. Reported-by: Luis Claudio R. Goncalves Fixes: "ptrace: fix ptrace vs tasklist_lock race" Signed-off-by: Oleg Nesterov Signed-off-by: Sebastian Andrzej Siewior Cc: stable-rt@vger.kernel.org Signed-off-by: Tom Zanussi --- kernel/ptrace.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 9c59e523f3cd..b7d2a22534da 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -207,8 +207,8 @@ static bool ptrace_freeze_traced(struct task_struct *task) static void ptrace_unfreeze_traced(struct task_struct *task) { - if (task->state != __TASK_TRACED) - return; + unsigned long flags; + bool frozen = true; WARN_ON(!task->ptrace || task->parent != current); @@ -217,12 +217,19 @@ static void ptrace_unfreeze_traced(struct task_struct *task) * Recheck state under the lock to close this race. */ spin_lock_irq(&task->sighand->siglock); - if (task->state == __TASK_TRACED) { - if (__fatal_signal_pending(task)) - wake_up_state(task, __TASK_TRACED); - else - task->state = TASK_TRACED; - } + + raw_spin_lock_irqsave(&task->pi_lock, flags); + if (task->state == __TASK_TRACED) + task->state = TASK_TRACED; + else if (task->saved_state == __TASK_TRACED) + task->saved_state = TASK_TRACED; + else + frozen = false; + raw_spin_unlock_irqrestore(&task->pi_lock, flags); + + if (frozen && __fatal_signal_pending(task)) + wake_up_state(task, __TASK_TRACED); + spin_unlock_irq(&task->sighand->siglock); } -- 2.36.1